GENETICS - BIOLOGY 202 MIDTERM Use the information below...

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BIOLOGY 202 MIDTERM VERSION 4 1 Use the information below to answer the next two questions: Assume that high blood pressure is inherited as an autosomal dominant trait. You genotype the individuals in your pedigrees with many markers and successfully localize the trait to a region on chromosome 3. A1 and A2 are two codominant alleles of the A marker gene on chromosome 3. Our representative family and their genotypes at the A marker are shown below. Note : Within a given generation, individuals are numbered consecutively from left to right (e.g., I-1, I-2 for the A1/A1 and A2/A2 parents in generation I). 1. (1 point) The individual(s) in the pedigree that has (have) produced informative meioses for mapping of the A marker and high blood pressure locus is (are): a. I-1 and I-2 b. II-3 c. III-2, III-4, and III-5 d. III-1 and III-3 e. None of the above Answer b. In order for an individual to produce informative meioses for mapping the disease and marker loci , it must be doubly heterozygous and produce progeny whose genotypes allow inference of the gamete type that was contributed by the individual in question (e.g., whether it was a parental or recombinant type of gamete). Given the information provided in the pedigree, we see that only II-3 fits these criteria. Note: Genotypes of individuals in generation III provide information for mapping, but it is not because of their meioses (i.e., we are not looking at the progeny of generation III!). 2. (2 points) Calculate a LOD score for linkage between the high blood pressure locus and marker A at a distance of 10 cM. a. 0.16384 b. -0.78558 c. -2.5406 d. -0.1835 2 e. None of the above Answer c. We must inspect the 5 testcross progeny present in generation III and consider the gamete types produced by II-3. Note that parental gametes of II-3 are either A1d or A2D (where D denotes the dominant disease allele), and recombinant gametes are A1D or A2d. Among the 5 testcross progeny, there is one that is the product of a
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BIOLOGY 202 MIDTERM VERSION 4 2 parental gamete of II-3 (individual III-3), whereas the remaining 4 progeny are each the product of recombinant gametes of II-3. Thus, the appropriate calculation of the LOD for 10 cM is: LOD = Log [(0.05 4 )*(0.45 1 )/.25 5 ] = -2.5406 (where Log denotes the base 10 log of the quantity in square brackets). 3. (1 point) In a complementation test the number of complementation groups indicates a. the number of genes required for a specific phenotype. b. the penetrance of the phenotype. c. the number of phenotypes for a gene. d. the number of chromosomes in an organism. e. the quantity of gene product required for a phenotype. Answer a. Use the information below to answer the next two questions: In a population, two different rare genetic diseases (extra finger and an eye disease) are observed. In the pedigree below (taken from a family in the population), a cross represents the occurrence of an extra finger and a black square represents the occurrence of the eye disease:
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This note was uploaded on 09/18/2011 for the course SCIENCE biol 200 taught by Professor Bureau during the Spring '11 term at McGill.

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GENETICS - BIOLOGY 202 MIDTERM Use the information below...

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